Final answer:
Year's disappearance in the poem underscores the fleeting nature of time and the inevitable progression of life that continues as time passes away.
Step-by-step explanation:
The sudden disappearance of Year in the poem adds meaning by highlighting the concept that time is ephemeral and transitions are seamless and often unnoticed. Year's departure signifies the inevitable progression of time and symbolizes the end of a cycle, which in turn makes room for a new beginning with the Babe (the new year). The cycle of the seasons within the poem mirrors life's constant, cyclical nature of change and renewal.
Therefore, the correct answer to how Year's sudden disappearance adds to the meaning of the poem is option C: It highlights the theme that while time passes away, life will continue on through time.